When I come face to face with the legend that is Dolly Parton in her lavish London hotel suite, she is confident, hilarious and a bundle of infectious energy.

Meeting her in the flesh is something else. With her bright blonde hair, famous 40DD assets and tiny, tiny waist, she looks every inch the superstar.

Dolly is elegant and well-presented with only a little evidence that the ravages of time are having any effect.

“I wear make-up and it gets a little bit thicker every year,” she joked only this week. “People say I look so happy – and I say that’s the Botox.”

But as Dolly, now 68, prepares to tour the UK this summer, including her first appearance at Glastonbury, we can reveal that behind all that front, behind the mask of make-up, she has hidden a lot sadness throughout her amazing 50-year career.

In an exclusive, never-before published interview, she tells me: “Depression runs in my family on both sides and I have to be wary. It’s usually brought on by something that’s going on in the family and if there are problems sometimes it’s a lot for one little person to carry.”

That she is beset with insecurities will comes as a surprise to fans who know her as the larger-than-life country singer with huge hits such as Jolene and 9 To 5.

“People are always saying to me I’m happy all the time,” she says. “But nobody is happy all the time. I am a tender-hearted person and I feel everything to the ninth degree. Every once in a while I just feel you know... sad-hearted and melancholy.

Overweight after a partial hysterectomy, her business was faltering and she was distraught that would she would never be able to have children.

She says quietly: “It was a really bad time and it took two years just trying to get my physical weight and hormones in order. That was the first moment in my life that I slowed down.

“But sometimes God just has to smack you down. He was almost saying, ‘Sit your pretty little ass down because we have to deal with some stuff.’?”

She believes that this harrowing time made her stronger in the end. “After that I was twice the person I ever was,” she says. “It was good for me. I didn’t drink or get on drugs but I saw where you could. I saw how people could get depressed enough to kill yourself.

“But I have a great faith, and if it gets to a point where I think I can’t quite handle it, I take it straight to God.”

Dolly is the first to admit she has had cosmetic surgery, but says the secret is not to take it too far. “I haven’t had to do anything for a long time if I’m honest,” she says. “Yes, I still have fillers, botox and collagen injections, but that’s about it.

“It’s true that if I see anything sagging I want to have it nipped and tucked straight away. But I try not to do anything drastic or have a lot of things done at once. That’s why I don’t look bad.”

There’s one part of her body she seems entirely content with.

She's got a lot of front: Dolly Parton (Image: Newcastle Chronicle)

“Years ago I said that my boobs were so famous I had them insured for a million dollars. A lot of people believed me though I was only joking. I’m not joking when I say they look like a million dollars though.”

However with any surgery and with implants in particular there are risks and the gossip mongers have always had a field day with Dolly’s surgically-enhanced pair.

One of the most dramatic stories said that silicon from her implants was dangerously leaking into her blood stream. At this, Dolly just lets off a raucous laugh.

“Honest to God, any work I have had done I’ve employed very professional people. And I have never had any problems with my implants,” she says.

“I have mammograms and check-ups all the time as well as MRI scans so they can have a good look.

“When they always say that my boobs are too heavy and are affecting my back, that’s not true either. I’ve always had big t**s even before my implants. I’ve just had them fixed and lifted, that’s all.”

Other rumours say Dolly’s long-term marriage to her “invisible” husband Carl is a sham and she is more than friends with her loyal personal assistant Judy Ogle, a friend since they were both growing up in the foothills of Tennessee’s Great Smoky Mountains. The speculation only intensified after Dolly once innocently admitted that they had shared the same bed.

“It doesn’t upset me but it upsets and embarrasses Judy and her family. I say to her which would you prefer – being called an old maid or a lesbian? She says lesbian every time!”

“We both went through high school together. She went into the military and when she came out of the army she never married. She dates and she has had several boyfriends. The fact that they never see my husband, they make it out that we are in a relationship.

“But I have never in my life had a ­relationship with a woman or had a desire to be with a woman.”

And what of Carl Dean, the man Dolly met in 1964 outside the Wishy Washy Laundromat in Nashville, Tennessee, and married two years later?

Some say theirs is an open relationship, and both partners – Dolly in particular – have enjoyed a string of affairs.

“Sometimes he goes to the grocery store and he sees a magazine with some story about me and he’ll get it and bring it home and say, ‘I see you’re having Burt Reynolds’s baby again’,” she says with a laugh.

“He has seen so much of it over the years. He’s not jealous and I’m not jealous of him. He knows I flirt. He flirts too. Yes, it’s an open relationship, but NOT sexually and I would kill him if I thought he was doing that. He would shoot me too. At the end of the day we love each other madly.”

Country legend: Dolly Parton performs in February in Melbourne (Image: Getty)

The fact that Carl never steps into the showbiz limelight, preferring to quietly run a road-surfacing business and potter around on the family farm is seen as evidence that their marriage is a sham.

But while it’s true that the only known pictures of them together are old, grainy and black and white, Dolly says there is no conspiracy.

“Listen, he’s a homebody and doesn’t like to go out in public,” she says. “We have a farm and he’s more than happy keeping the fields mowed, the barns painted and working away on his farm equipment

They have never even had a serious row, she says. “We might get a little moody or testy once in a while and he might go to the barn and I might go into the office, but we never argue.”

Dolly says she always dresses up for Carl at home to keep the romance alive.

“Even when I am wearing comfortable clothes, not my stage clothes, they are still kind of cute and sexy,” she tells me.

Dolly says that in private her husband is a hopeless romantic who loves to shower her with surprise gifts.

Beaming from ear to ear, her eyes light up as she remembers: “Come springtime in Tennessee, we have buttercups coming up around the side of the barn and last week he brought me a little mason jar full of them and wrote me a little poem.

“On Valentines day he’s always writing little poems such as ‘Roses are red, violets are blue. I wrote this little poem for you’ ... he just writes cute things.

“He always brings me wild flowers when they first bloom on the farm and will always sit them on my make-up station.

“Listen, my husband is a great guy and is so proud of me. He gets such a kick with people getting a kick out of me.”